INES Mapper 027

iNES Mapper 027 is believed to be an pirate variant of the VRC4 mapper.

GoodNES thinks this is used for World Hero.
We should discover whether this mapper number is used for any other unlicensed/pirate/multicart VRC2/4 games.

This is supported by BizHawk as of r3975 and FCEUX for some time prior but definitely as of 26-nov-2012.

Formerly FCEUX emulated this with unique code, but as of r2722 CaH4e3 asserts that it is a duplicate of INES Mapper 023.
This means the only difference between 27 and the other VRC4 mappers (21, 23, and 25) is the way the board wires up the address lines.
However, FCEUX's VRC2/4 emulation is filled with hacks for pirate and multicart games which are otherwise similar to VRC2/4.

In particular, World Hero depends on the VRC4's 9-bit CHR bank numbers, where the most significant nibble of the CHR banks are actually 5 bits.

The below notes are left until the author agrees they are describing VRC4: